Evaluation of Liquid Crystals, Dot Fluids, and Compliant Coatings for Hydrodynamic Flow Visualization on Surfaces.

Abstract : Three new approaches to hydrodynamic flow visualization on surfaces were evaluated: shear-sensitive liquid crystals, high-viscosity dot fluids, and optically monitored compliant coatings. Liquid crystal mixtures were highly successful, producing high-resolution observations of both steady and unsteady boundary layer separation and transition characteristics. Dot fluids of high viscosity were not superior to low-viscosity fluids thickened with pigment, but minor differences in behavior occurred among the four base fluids used. Optical methods of detecting shear- or pressure-induced displacements of compliant coatings were unsuccessful in a water tunnel environment.